Method of recovering metals.



W. 0. SNBLLING.

METHOD 0F RBGOVBRING METALS.

APPLICATION FILED SEPT.1B, 1908.

Patented Apr. 6, 1909,

l iN

trimaran srnrns riarnivr onmon WALTER O. SNELLING, OF PITTSBURG,PENNSYLVANIA.

METHOD 0F RECOVERIIING- METALS.

Application led September 18, 1908.

T 0 all 'whom 'Lt may concern:

Be it known that I, WALTER O. SNELLING, a citizen of the United States,residing at Pittsbur in the county of Allegheny and State of ennslvania, have invented certain new and usefullmprovements in Methods ofRecovering Metals, of Which the following is a specification.

The object of this invention is the provision of a method of recoveringmetals, in elemental form or as solutions, from their ores, and moreparticularly from electricallycollductive ores. The method is especiallyadapted for the production of metallic tin from cassiterite and will bedescribed by reference to this particular a plication. The method ishowever genera ly applicable to such ores as are reducible at thecathode in an electrolyte capable of liberating hydrogen.

-According to my method the ore, as cassiterite, in suitably subdividedform or in its naturally occurring forms as stream tin, Wood' tin, etc.,is disposed in contact with an electrode in an electrolyte capable ofliberating hydro en. Upon passage of a suitable current re uction of theore occurs and a part or all of the metal is set free: thereafter thereduced metal is constituted the anode in the same electrolyte, and themetal is dissolved therein and is either deposited upon a suitablecathode, or under suitable conditions is retained in solution.

It will be understood that While in operations of this class thereduction proceeds at first with a high degree of efficiency, thisefficiency tends to fall as the operation proceeds, the fall ofefficiency being proportionate to the amount of current passing directlyto the reduced metal instead of to the unreduced ore. This tendency toreduction of eiiciency after the first moments of the operation existsin all cases, but is more pronouncedinthe treatment of such compounds asare relatively difficult of reduction, easily reducible compounds beingmore efficient as depolarizers. If the current were melf y reversed inthe solution after a certain quantity of metal had been reduced at ythecathode, and a ain reversed when this reduced metal had gbeen dissolvedand redeposited, no useful purpose Would be served, for the metaldeposited u on the initial anode Ywould be again dissolved? Therefore inproceeding according to this plan it becomes necessary to remove thedeposited metal at the close of each cycle of operations, and such pro-Specication of Letters Patent.

Patented April 6, 1909.

Serial No. 453,607.

cedure is costly and troublesome when the reversals are made at shortintervals as is'reuired for high efficiency. I prefer thereore toprovide in the bath a third vor intermediate electrode and to so shiftthe current connections that one of the three electrodes is at all timescut out of circuit. As hereinafter described, this arrangement permitsthe cycles to be of very short durationif desired, Without hovfeverrendering it necessary to remove the deposited metal at correspondinglybrief intervals.

Apreferred form of apparatus for carrying out my invention is shown inthe accompanying drawing wherein the figure is a vertical section of anelectrolytic vat, the circuit connection being diagrammaticallyillustrated.

ln said drawing l represents a tank or vat consisting of or lined Withinsulating material adapted for use with the electrolyte selected, and2, 3, 4, the electrodes therein, the electrode 3 being intermediate ltheeX- terior electrodes 2, 4.

5 is a circuit-changing switch which may be of any usual type.

l6, 7 re resent respectively the positive and negatlve leads from avdirect current circuit of loW potential.

Assumin the electrolyte to consist of hydrochloric acid, the severalelectrodes may consist of raphite: in case sulfuric acid is employed,lead may be used: or a suitable alkaline electrolyte, as caustic soda orsodium stannate, may be employed, in Which case the electrodes may be ofiron. The plate 2 serves as the anode during the reducing stage, and theperforated plate or screen 3, or the charge thereon in case the ore isconductive, as the initial cathode. When the switch is in the positionshown in full lines the current will traverse the bath in such directionas to effect the reduction of the ore, as will be readily understood. WVhen the eiciency of this reduction shows a material decrease as Will bethe case after the exposed surfaces-have been reduced to metal, theswitch is moved to the position indicated in dotted lines, whereupon thecurrent Will pass from the reduced metal in electrical connection Withthe late 8 to the plate or pan 4 as cathode, issolving the metal andredepositing it. Inasmuch as the reduced metal, as tin, is soluble Whenconnected as anode in the electrolyte chosen, While the material of theplate or screen 3 is insoluble therein, under proper current conl 'E l10 electrode 4, functioning as cathode during the precipitation, mayconvenientlyT be constructed 1n the form of a shallow removable an asshown to retain metal deposited in oose or non-adherent form.

It will be observed that in the particular arrangement of apparatusdescribed the electrode 2 serves intermittently as anode, and theelectrode 4 serves intermittently as cathode, lwhile the intermediateelectrode functions alternately as cathode and as anode, the oreundergoing reduction during the irst eriod and the reduced metal beingdissolve and redcposited during the second eriod. Automatic means may beemployed 5 or shiftin the current connections at inter vals suite to thenature of the ore and the character of the current ern loyed, and theprocess may readily be rencred essentially continuous in character. Itwill be4 obvious 80 that the disposition and arrangement of theapparatus may be widely varied without.

departure from the spirit of my invention. 1n case 1t is desired toproduce a solution of a metallic salt, for example stannous chlorid,instead of the metal, this may be accomplished by providing an acidelectroe lyte, e. e. hydrochloric acid, of such concentration as toprevent substantial deposition of the metal during the period that thereduced ore functions as anode.

I claim:

1. The method of recovering metals from their compounds which consistsin disposing such compounds in connection with an electrode in asuitable electrolytic bath and reducing portions of the compound tometal, and thereafter connecting said metal as an-v ode in said bath todissolve the reduced metal.

2. The method of recovering metals from their compounds which consistsin disposing such compounds in connection with an elec- 'trode in asuitable electrolytic bath and reducing portions of the compound tometal,

and thereafter connecting said metal as anode in said bath 'to dissolvethe reduced metal and re-deposit the same.

3. The method of recovering metals from electrically conductivecompounds which 6 0 consists in connecting such compound as cathode in asuitable electrolytic bath, reduclng portions of the compound to metal,and

thereafter connecting said metal as anode in said bath to dissolve thereduced metal and re-deposit the same.

4. .'l'hc method of recovering tin from its oxid orcs which consists indisposing such ore in connection with an electrode in a suitableelectrolytic bath, reducing portions of said oxid to metal andthereafter connecting` said metal as anode in said bath to dissolve thetin.

5. The method of-recovering tin from its loxid ores which consists indisposing such orc in connection with an electrode in a suitableelectrolytic bath, reducing portions of said oxid to metal andthereafter connecting said metal as anode in said bath to dissolve thetin and re-deposit the same.

6. The method of recovering tin from its conductive oxid whichconsistsin connecting the oxid as cathode in a suitable aqueous electrolyte, andelectrolytically reducing said oxid.

'7. The method of recovering metals from their compounds which consistsin providing in contact with a suitable electrolyte an electricallyintermediate and two electrically exterior' electrodes, arranging thecompound of the metal in contact with the intermediate electrode,reducing the same by passing an electric current from one of theexterior electrodes as anode, and then shifting the point of supply ofcurrent to redissolve said metal and deposit the same on the other ofsaid cxterior electrodes.

8. The method of recovering tin from its conductive oxid which consistsin providing in contact with a suitable electrolyte an electricallyintermediate and two electrically exterior electrodes, disposing theoxid in contact with the intermediate electrode, reducing the same bypassage of an electric current from one of the exterior' electrodes asanode, and then shifting the point of supply of current to redissolvethe tin.

9. The method of recovering tin from its conductive oxid which consistsin providing in contact with a suitable electrolyte an electricallyintermediate and two electrically ex-. terior electrodes,A disposing theoxid in contact with the intermediate electrode, reducing the same bypassage of an electric current from one of the exterior electrodes asanode, and then shifting the point of supply of cnrrent to redissolvethe tin and deposit the same on the other of said exterior electrodes.

In testimony whereof, l afi-ix my signature in presence of twowitnesses.

VVA'LTER O. SNELLING.

`W'tnesses:

A. L. HYDE, -HUeo ScnLATTnn.

